The physical properties of Kondo insulators SmB6 and FeSb2
| Autor: | Fang, Shin-Hung, 方新鴻 |
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| Rok vydání: | 2014 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 102 SmB6 and FeSb2 are 4ƒ and 3d Kondo insulators respectively, their resistivity increases as temperatures and saturates below 6 K. Recently, it is indicated that Kondo insulator SmB6 also exhibits topological properties that the in-gap state observed by ARPES to explain the saturation in resistivity at low temperatures. Therefore, SmB6 has been called topological Kondo insulator (TKI). In narrow band gap semiconductor FeSb2, 3d orbit of Fe hybridizes with s-p orbit of Sb to form the hybridization band. Since the Fermi level lies in the gap, the resistivity also shows the semiconductor behavior. In this thesis, SmB6 and FeSb2 crystals were prepared by chemical vapor transport (CVT) and flux method respectively for the study of physical properties by electrical and magnetic measurements. FeSb2 also shows the saturation in low temperature resistivity as similar to SmB6, showing the saturation in resistivity caused by surface state. Therefore, FeSb2 is also identified as one of TKI. Through the data of temperature dependent resistivity, two transport gaps 2.67 meV and 37.31 meV are calculated. Above 60 K, magnetism is contributed by the thermal activated electrons which jump to the spin gap of 38.95 meV. Below 60 K, there is an upturn in magnetic susceptibility which is caused by the magnetic impurity. In order to observe the surface state, thin film is the better choice. We made FeSb1.75 thin film by pulsed laser deposition (PLD). In resistivity measurements, the thin films which were deposited more than 2 hours were observed the saturation below 10 K and two transport gaps. The both behaviors are similar to single crystal of FeSb2. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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